Smithsonian Institution

President Barack Obama heralded a new national black history museum as “not just a record of tragedy, but a celebration of life” as he marked Wednesday’s groundbreaking of the long-sought-after museum on the National Mall.

In the bowels of the Museum of Nature & Science in Fair Park, Tommy Diamond sat hunched over what looked like a huge boulder of plaster. He spends eight hours (or more) a day chipping away at the vertebra of an Alamosaurus.